Why does a thyristor keep conducting after removing the gate current?

Click For Summary

Discussion Overview

The discussion revolves around the operational characteristics of thyristors, particularly why they continue conducting after the gate current is removed, contrasting this behavior with that of transistors. Participants explore the underlying principles and equivalent circuit models of thyristors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express confusion about the fundamental operation of thyristors compared to transistors, noting that while transistors turn off when gate voltage is removed, thyristors remain on due to current flow.
  • One participant mentions "SCR Latchup" and refers to an equivalent circuit of a thyristor, suggesting this might clarify its operation.
  • Another participant attempts to explain the thyristor's behavior by referencing its structure as a PNPN device, likening it to two transistors connected in a specific configuration.
  • There are repeated assertions about the inability to remove contact between certain layers of the thyristor, although the reasoning behind this is not universally understood among participants.
  • One participant admits to a lack of understanding of thyristors despite extensive experience in electronics, indicating a broader uncertainty about the component.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the explanation of thyristor operation. There are multiple competing views and ongoing confusion regarding the comparison with transistors and the implications of the PNPN structure.

Contextual Notes

Some limitations in understanding are evident, particularly regarding the assumptions about the thyristor's structure and operational principles. The discussion reflects varying levels of familiarity with the topic among participants.

Who May Find This Useful

Individuals interested in electronics, particularly those seeking to understand the operational principles of thyristors and their comparison to other semiconductor devices.

brent1369
Messages
9
Reaction score
0
i have seen several videos of thyristors but they never really explain the fundamentals
they just say that cause there is a current flowing in there it keeps being on
but why does a transistor then turn off when you remove gate voltage
 
Engineering news on Phys.org
brent1369 said:
i have seen several videos of thyristors but they never really explain the fundamentals
they just say that cause there is a current flowing in there it keeps being on
but why does a transistor then turn off when you remove gate voltage
Have you learned about "SCR Latchup" yet? Are you familiar with this view of the thyristor equivalent circuit? :smile:

https://www.electronics-notes.com/images/thyristor-scr-equivalent-circuit-01.svg

1588098915578.png


https://en.wikipedia.org/wiki/Latch-up
 

Attachments

  • SCR Latchup Thyristor.png
    SCR Latchup Thyristor.png
    5 KB · Views: 258
Last edited:
  • Like
Likes   Reactions: davenn and cnh1995
I understand it when you divide it in 2 transistors but not when its 1 whole thyristor
 
Last edited by a moderator:
Cause you can't remove contact with highest P and highest N of th 2
and also lowest N and lowest P of th 1
 
Last edited by a moderator:
  • Informative
Likes   Reactions: etotheipi and davenn
berkeman said:
Sorry, I can't parse that. A thyristor is just a PNPN structure, which is basically the same as the two transistors connected in the stacked format that I showed previously.

https://www.theengineeringprojects.com/wp-content/uploads/2019/11/what-is-thyristor.jpg

View attachment 261674

Thanks for the heads up :smile:

Gosh, in the 50 odd years of doing electronics, the thyristor is probably one of my least understood
component. Not having had any real need to use them, has lead to some ignorance of them.Dave
 
  • Like
Likes   Reactions: berkeman

Similar threads

Is My Thyristor Gate Driver Circuit Malfunctioning Due to Component Issues?
  • · Replies 12 ·
Replies
12
Views
2K
Why is the drain current steady after pinchoff in a JFET?
  • · Replies 1 ·
Replies
1
Views
4K
Why does the SCR remain 'ON' even though the gate pulse is removed?
  • · Replies 1 ·
Replies
1
Views
3K
How does an open collector work?
  • · Replies 8 ·
Replies
8
Views
3K
Does Drain Current Increase if Doping Increases?
  • · Replies 5 ·
Replies
5
Views
2K
Extremely high current effects in semiconductors
  • · Replies 11 ·
Replies
11
Views
3K
Need help in understanding these circuits
  • · Replies 2 ·
Replies
2
Views
2K
Why Choose IGBT Over MOSFET for Low-Frequency Applications?
  • · Replies 10 ·
Replies
10
Views
7K
Why and by how much does unbalanced current flow increase EM radation?
  • · Replies 9 ·
Replies
9
Views
2K
Transistor Logic Gate : NOT Gate Explanation?
  • · Replies 9 ·
Replies
9
Views
4K